1. Field of the Invention
This invention relates to a stroboscopic discharge tube, particularly to such discharge tube for use in photography.
2. Prior Art
It has been a common practice in the art of photography to use a stroboscopic discharge tube to make up for an insufficiency in the amount of light for exposure of the photographic film. The discharge tube is energized by electric current of 100 to 3,000 amperes, usually about 1,000 amperes to emanate light. The prior art stroboscopic discharge tube generally comprises a glass tube having its opposite ends closed, a cathode and an anode disposed in the tube, and a plasma producing gas sealed in the tube, said cathode comprising an electric conductive stem extending through one end of the tube into the tube interior and an annular ring formed of emissive material secured to the stem by firmly caulking the ring to the latter, said anode comprising a conductive stem alone extending through the other end of the tube into the interior, the diameter of said ring being such that the outer periphery of the ring is substantially spaced from the inner wall of the tube.
It has been found, however, that the conventional discharge tube has the serious drawbacks that the amount of the lighting level or luminous intensity is unstable, varying from discharge to discharge and that such discharge tubes have unevenness in quality, providing different luminous intensities from product to product. Thus, in some instances an adequate amount of light is not provided, and in some instances the lighting abruptly rises to an excessively high peak level and then rapidly diminishes, so that the photographic film in current use is not capable of capturing enough light to produce clear colors. Particularly, the self-developing, so-called "instant" film was unable to produce distinct colors with the prior art stroboscopic discharge tube. Moreover, the discharge tube had the disadvantages that when the discharge tube is adapted to a so-called automatic stroboscopic camera in which the amount of light emanating from the discharge tube is automatically controlled, a light receiving element which senses the amount of light from the discharge tube will give false instructions due to the instantly excessive high level of the light, thus resulting actually in deficiency of light amount.